Measuring the concentration of substances, particularly in the presence of other substances, is important in many fields. This is especially true in medical testing and diagnosis. For example, the measurement of glucose in body fluids, such as blood, is crucial to the effective treatment of diabetes.
Multiple methods are known for measuring the concentration of analytes, for example glucose, in a blood sample. Such methods typically fall into one of two categories: optical methods and electrochemical methods. Optical methods generally involve reflectance or absorbance spectroscopy to observe the spectrum shift in a reagent. Such shifts are caused by a chemical reaction that produces a color change indicative of the concentration of the analyte. Electrochemical methods generally involve, alternatively, amperometric or coulometric responses indicative of the concentration of the analyte. See, for example, U.S. Pat. No. 4,233,029 to Columbus, U.S. Pat. No. 4,225,410 to Pace, U.S. Pat. No. 4,323,536 to Columbus, U.S. Pat. No. 4,008,448 to Muggli, U.S. Pat. No. 4,654,197 to Lilja et al., U.S. Pat. No. 5,108,564 to Szuminsky et al., U.S. Pat. No. 5,120,420 to Nankai et al., U.S. Pat. No. 5,128,015 to Szuminsky et al., U.S. Pat. No. 5,243,516 to White, U.S. Pat. No. 5,437,999 to Diebold et al., U.S. Pat. No. 5,288,636 to Pollmann et al., U.S. Pat. No. 5,628,890 to Carter et al., U.S. Pat. No. 5,682,884 to Hill et al., U.S. Pat. No. 5,727,548 to Hill et al., U.S. Pat. No. 5,997,817 to Crismore et al., U.S. Pat. No. 6,004,441 to Fujiwara et al., U.S. Pat. No. 4,919,770 to Priedel, et al., and U.S. Pat. No. 6,054,039 to Shieh, which are hereby incorporated in their entireties.
A sample-receiving portion of the testing apparatus typically controls the geometry of the blood sample. In the case of blood glucose meters, for example, the blood sample is typically placed onto or into a disposable test strip that is inserted into a test meter. In the case of electrochemical test meters, electrical signals must be transferred between the meter and the test strip and vice versa.
Test system designers desire to minimize the size of the sample required for accurate measurement in order to improve the user experience. The resulting test sensor and test strip miniaturization has resulted in the use of thin film test strip patterns comprised of noble metals deposited on plastic substrates, such as by plating and subsequent laser ablation, to form the electrodes and associated connector contact pads of the test strip. These techniques allow for improved edge quality and improved dimensional resolution of the metallized features on the test strip. Such thin film coatings are highly prone to scratching by current commercially available connectors. Therefore, reducing abrasion between the test strip contact pad and meter connector contact wire is especially important in biosensor designs. Repeat insertions of the test strip (two to four times) can render these thin film coated biosensors useless. Even the first-time insertion of the test strip into the test meter may cause some removal of these thin film coatings by the test meter connector. The result is a less reliable connection between the contact pad on a test strip and the connector contact wire in the test meter.
Reducing abrasion between the test strip contact pad and meter connector contact wire is also important for longevity of the test meter. A typical test meter may have a life cycle requirement of over 10,000 test strip insertions. During normal use, a single test strip may be inserted and removed from the meter several times before the test is successfully performed. Abrasive contact between the connector contact wire and contact pad can reduce the longevity of the test meter connector, thereby further reducing the reliability of the system. Some biosensor systems are designed for use by consumers, who sometimes put still further stresses on the test system by using the system in environments at the margins of its design specifications, such as in high-humidity environments, or exposing the device to air containing corrosive components.
Thus, there is a need for further contributions and improvements to biosensor system technology, including connectors that provide improved performance and resistance to abrasion of test strip contact pads and meter connector contact wires.